Ownership: Weibo is owned and controlled by Sina Corp. which has 77% of the shares. Alibaba group, a Chinese e-commerce company, invested $585.8 million and owns 18% of the company, with an option to increase its stake to 30%. (Yahoo owns 24% of Alibaba.)

Revenues in 2013: $188 million, up 185%. (Twitter by contrast got $665 million in the same period.)

Weibo's Alibaba alliance will bring it $380 million in revenues through 2015.

Weibo is holding $246 million in cash on its balance sheet.

Weibo can be shut down by the Chinese government any time if it "impairs the national dignity of China."

Weibo must also register its encryption software with the Chinese government.

The company is officially registered in the Cayman Islands in order to avoid lawsuits.

Here's Weibo's income statement (click to enlarge):

Historic user growth:

Weibo daily user activity:

The filing also has some useful information on the web in China generally. Here is a chart of internet penetration in China. You can see how much room Weibo has to grow — the Chinese population is 1.3 billion.

This chart shows internet ad spending in China, which is now up to $15 billion a year.

Here's an example of how Weibo posts go viral. A passenger on the jet that crashed in San Francisco last year uploaded some of the first pictures to Weibo. Chinese TV news stations used the pictures in their reporting.